Media noise suppression and thermal stability remain key challenges to extending magnetic recording technology beyond the currently achieved areal densities. Future density advancements may require magnetically harder materials and, as a consequence, larger write fields. It is also known that in order to exploit the potential of magnetically harder materials a finer grain structure with properly decoupled grains and tight control of magnetic and physical grain size distributions are required.
Perpendicular magnetic recording employing magnetic media comprising a hard magnetic recording layer and a soft magnetic underlayer is evolving as a follow-on technology to current longitudinal magnetic recording systems. There are currently very few media and materials technology options in light of the stringent boundary conditions imposed by thermal stability and signal-to-noise requirements which must be met in order to extend perpendicular magnetic recording to areal densities beyond 80 or 100 Gbit/in2. Although significantly higher areal densities are theoretically achievable in perpendicular magnetic recording systems, such densities may only be achieved if the grain-count per bit is drastically reduced, e.g., from currently about 80 grain-count per bit (based upon an areal density of 100 Gbit/in2; 35 nm×180 nm bit cell; 750 kfci×150 ktpi; and 10–15% channel overhead) to as low as 10 grain-count per bit (based upon an areal density of 500 Gbit/in2; 11 nm×47 nm bit cell; 1850 kfic×540 ktpi; and greater than 35% channel overhead). However, such increased areal densities will lead to higher relative media noise and will require significantly improved channel detectors, with associated large error-correction overhead.
In order to achieve significantly improved areal densities with perpendicular magnetic recording media, the magnetic cluster size needs to be reduced, e.g., to about 8 nm, and the grain size distribution should be trimmed, e.g., below about 10 percent (sigma over mean). Current state-of-the-art sputtered media have grain size distributions of about 25 percent. It remains a major challenge to achieve the grain distribution target using current thin film sputtering processes and materials.
A need therefore exists for perpendicular magnetic recording media having enhanced signal-to-noise ratios and sufficiently high thermal stabilities.